fix: docker/test/ubuntu-16.04-latest/Dockerfile to reduce vulnerabili…

…ties

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-UBUNTU1604-BASH-542609
- https://snyk.io/vuln/SNYK-UBUNTU1604-DPKG-2848000
- https://snyk.io/vuln/SNYK-UBUNTU1604-E2FSPROGS-2770734
- https://snyk.io/vuln/SNYK-UBUNTU1604-GZIP-2442559
- https://snyk.io/vuln/SNYK-UBUNTU1604-SYSTEMD-1320131

docker/test/ubuntu-16.04-latest/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:16.04
+FROM ubuntu:xenial-20210416
 RUN sed -i -e 's/http:\/\/archive/mirror:\/\/mirrors/' -e 's/\/ubuntu\//\/mirrors.txt/' /etc/apt/sources.list
 RUN sed -i -e 's/http:\/\/security/mirror:\/\/mirrors/' -e 's/\/ubuntu\//\/mirrors.txt/' /etc/apt/sources.list
 RUN apt update && apt install -qqy dos2unix ca-certificates curl software-properties-common lsb-core sudo vim systemd gawk git wget